Plum Pie with Almond Meringue Crust

Name: Plum Pie with Almond Meringue Crust
Ingredients: Cooking spray; 3/4 cup unsalted roasted almonds; 3 large egg whites, at room temperature; 1/4 teaspoon cream of tartar; 3/4 cup superfine sugar; 1/2 teaspoon baking powder; 1/4 teaspoon pure almond extract; 3/4 teaspoon unflavored gelatin powder (from a 1/4-ounce packet); 1/4 cup plus 1 tablespoon water; 1 1/2 pounds ripe plums (about 5); 2/3 cup plus 1 tablespoon granulated sugar; Pinch of salt; 1/4 cup cornstarch; 3/4 cup cold heavy cream; 2 tablespoons sour cream; 1/2 teaspoon pure vanilla extract